and engineers, however, agree that open-hearth steel of a given composition is more reliable, more -uniform, and less liable to break in service than Bessemer -steel of the same composition. And there are many metallurgists and engineers both in this country and abroad who believe that acid open-hearth steel is. more reliable than basic open-hearth steel of similar composition. In Chapter XVII it will be shown that there is mathematical evidence to support this opinion.
A fact bearing upon this question is that in Germany there are two companies which make a business of special steel for forgings, tools, etc., etc. These companies use acid Bessemer steel for this work, although basic steel is cheaper. They are the only makers of acid steel in the great Ruhr district, and the basic Bessemer works do not invade their lines of business. This would indicate a belief in the superiority of the acid product.
THE BASIC OPEN-HEARTH PROCESS.
The term basic open-hearth furnace means a regenerative gas furnace, used for melting steel and lined with basic material, usually either magnesite or burned dolomite.
It has been stated in discussing the acid open-hearth that the bottom itself takes very little part in the operation, but that it determines the character of the slag that can be carried. When the bottom of the furnace is made of silica (sand) the slag must be silicious; but when the bottom is basic the slag must be basic. Consequently in the basic open-hearth furnace the charge is composed of pig-iron and scrap, just as in the acid furnace, but, in addition to this, a certain amount of lime or limestone is .added. The whole mass of iron, scrap and lime is melted down by the action of the flame. The silicon and carbon of the pig-iron are oxidized, just as in the acid process; the manganese of the scrap and some of the iron are both oxidized just as on the sand bottom; but the silica and the oxides of iron and manganese do not make a slag by themselves, for they unite with the lime that has been added. This gives a basic slag, and when the slag is basic the phosphorus in the pig-iron and scrap will be oxidized and enter the slag as phosphate of lime or iron, just as it does in the basic Bessemer vessel. Thus the basic open-hearth furnace will allow the purification of iron con-